1. Field of the Invention
The invention relates to an energy-saving drive apparatus for DC loads, and more particularly to an energy-saving drive apparatus that ensures a full use of power by the control of an energy converter for achieving the energy-saving effect.
2. Description of the Related Art
Both the light energy and the electric energy are indispensable for the modern life. For example, the outdoor Christmas lamps require an electric cord for transmitting the electric energy to the lamps for lighting purpose. Moreover, many objects in our daily life also require electric energy. They are ready and practical for indoor use when they are connected via electric cords to mains socket. To the contrary, they can be problematic when used outdoors since they require a very long extension cord. Among these objects, they may require a mini motor as drive source. It is a time-wasting and labor-wasting task to establish an electric connection between the mini motor and the mains socket by the electric cord. Besides, the electric cord will destroy the appearance of the environment.
Therefore, many products are designed in such a way that they are driven by batteries. However, the batteries have the restricted service life. When they are used as power source for feeding current to loads like the outdoor lighting source, mini motor, etc. the battery will rapidly be exhausted. This does not meet the economic benefit. However, there are many loads that are used outdoors and driven by low voltage and current. To fit them with an energy-saving drive circuit for minimizing their loss and achieving the power-saving effect will meet the requirement of economic benefit no matter if primary, secondary or solar batteries are used as power source. In this way, a convenient, safe, and eco-friendly use is guaranteed.
For example, the semiconductor diode is one of the basic components in the electronic system. Its application scope can range from simple to complicated field. The rectifying function of the household appliances, for instance, is achieved by the one-way on-state function of the diode. Besides, the back light module of mobile phones and LCDs, the outdoors Christmas light, advertising board, traffic light, etc. make use of LEDs. Therefore, the LED becomes a very important light-emitting apparatus. In addition, LEDs have the advantages of small volume, low power consumption and prolonged service life. In near future, the LEDs may replace the conventional bulbs as lighting source.
However, high temperature will be created when LEDs light up for a long time, thereby affecting the luminance (Lu). Previously, the way to light up the LEDs is to directly feed the DC current to the LEDs. Thereafter, the LEDs give out visible light when excitated. LEDs are mainly made of GaAsP or GaP. The wavelength and the color of the emitting light is different depending upon material used. For example, the LEDs made of GaAsP emit the red light while the LEDs made of GaP emit light in color between yellow and green. As shown in FIG. 1A, the luminous intensity of the light emitted by LEDs is directly proportional to their on-state current. Thus, as shown in FIG. 1B, the luminance (Lu) is adjustable according to the input low (L) DC current (I) or the input high (H) DC current (I). However, high temperature will be created in a short time by lighting up LEDs for a long time. Accordingly, the luminance of LEDs will be lessened when a suitable cooling device is not available, thereby reducing their operational reliability.
Furthermore, some DC loads like mini-motors used as power source for certain products don't achieve the expected power efficiency since the DC power source can't ensure a voltage and current impedance matching of the load at the output terminal according to the load features for minimizing the loss.
How to resolve the problems of the above-mentioned DC loads like lighting sources or mini-motors is the main topic of the invention.